1. Field of the Invention
The present invention relates to an absorbent article suitable for absorbing menstrual blood and so on discharged from a woman's genital organ, more particularly, relates to an absorbent article having a liquid acquisition layer between a topsheet and a liquid absorbent layer so as to absorb liquid and introduce it into the liquid absorbent layer.
2. Description of the Related Art
Absorbent articles intended to absorb menstrual blood discharged from a woman's genital organ are typically constructed to include a liquid-permeable topsheet appearing on its skin surface, a liquid-impermeable backsheet appearing on its garment surface and a liquid absorbent layer disposed between the topsheet and the backsheet, and generally, they are worn with the backsheet adhered to an inner side of a groin piece of an undergarment through a pressure-sensitive adhesive layer.
In such an absorbent article, if a large amount of menstrual blood is given to the topsheet at a time, menstrual blood remains in the topsheet for a long time, making a wearer uncomfortable due to wet feeling in the crotch. Therefore, there have been known absorbent articles devised to diffuse or retain liquid beneath the topsheet when a large amount of liquid is given thereto at a time.
Japanese Unexamined Patent Publication No. 6-38998 (Patent Publication 1) discloses a sanitary napkin in which a liquid transferring band is disposed between the topsheet and the liquid absorbent layer.
The liquid transferring band is nonwoven fabric formed with a screen pattern of a large number of recesses. The screen pattern is composed of an embossed pattern, in which high fiber density portions are formed by compressing a given thickness of nonwoven fabric from one side, and an embossed pattern, in which membrane portions are formed by compressing the nonwoven fabric from both sides, wherein both embossed patterns are arranged in a longitudinal (lengthwise) direction of the sanitary napkin. In the liquid transferring band, movement of menstrual blood having passed through the topsheet is restricted by the membrane portions so that the menstrual blood can be diverted and introduced into the high fiber density portions, thereby diffusing menstrual blood in the longitudinal direction so as to prevent liquid from being left in the topsheet.
On the other hand, Japanese Unexamined Patent Publication No. 2000-140015 (Patent Publication 2) discloses a disposable diaper in which a liquid permeable sheet is disposed between the topsheet and the liquid absorbent layer.
This liquid permeable sheet is nonwoven fabric or paper that is three-dimensionally deformed to have a large number of recesses defined by projections extending in a net-like pattern. This disposable diaper is intended to prevent liquid from flowing along a surface of the diaper by temporarily retaining liquid in the recesses formed in the liquid permeable sheet even when a large amount of liquid is applied at a time.
In the liquid transferring belt disclosed in Patent Publication 1, liquid having passed through the topsheet can be diffused in the longitudinal direction, but because the liquid transferring belt itself is inferior in both liquid retention ability and liquid permeability, the liquid transferring belt will be immediately saturated if a large amount of menstrual blood is applied thereto, easily causing the problem of liquid residue. In detail, the liquid transferring belt is meltblown nonwoven fabric formed with an embossed pattern, wherein since the meltblown nonwoven fabric remains relatively flat even after embossing, a large amount of liquid locally applied thereto cannot be retained. Furthermore, since recesses forming the embossed pattern in the nonwoven fabric are of an extremely small space volume, little liquid will be retained in the recesses. Rather, the meltblown nonwoven fabric is inferior in liquid permeability not only because such meltblown nonwoven fabric itself is of a high density but also because the membrane portions block liquid permeation.
On the other hand, the liquid permeable sheet disclosed in Patent Publication 2 is intended to retain urine in triangular recesses so as to prevent diffusion along the sheet. However, since liquid diffusion is inhibited by the net-like projections, the recesses will be saturated with urine in a short period of time. Accordingly, if the liquid permeable sheet is adopted for sanitary napkins, menstrual blood that is thicker than urine will be easily left in the recesses. Moreover, Patent Publication 2 teaches that the liquid permeable sheet is preferably formed of paper, but if such a liquid permeable sheet formed of paper is adopted for sanitary napkins, the recesses will be immediately crushed by a pressure applied from the wearer's crotch and the liquid permeable sheet will be easily broken when an offset force acts on the sanitary napkin.